Chests

Chests are an uncommon drop from your opponent's creatures once they are destroyed, and can also be bought using coins or gems from the main screen. Each chest has a single card in it, which will vary in rarity and strength depending on the kind of chest.

This chest can be bought for 10,000 Coins. It will supply either a 1, 2, 3, 4 or 5 star rarity card. It's not necessarily worth purchasing, since most of these cards aren't worth the coins you spend, and can be obtained later on for free. However, it is a good way to obtain unique cards and save time getting cards for crafting, should you have excess coins that you don't mind using.